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Bike Hacking (aka "Bicycle Autopsy") - Section 4

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Photo 33 - Bearings, cup and axel can now be removed.

Notice the direction the bearing are facing — balls up, ring down. If you try to put it back together in reverse, it will not work. If bearings fell all over the bench, this means the rings have corroded and the bearings are no good. Check the rings for cracks or excessive wear, and toss them if they show any signs of damage. Also check the threads in the bottom bracket. All that is left is the drive side ring, and for this you will need your large wrench or pipe wrench again.

Take note that this side is reverse thread; you will be turning it clockwise to loosen it (Photo 34). Sometimes this ring can be really stuck from rust and dirt, so you may need your entire army of tools — wrench, hammer, blowtorch — to get it out.

Photo 34 -Removal of the right-side bearing cup in the clockwise direction.

You will notice that there is not much of the ring above the bracket. Make sure the wrench is set perfectly or you will slip, or round off the edges. A little heat directed at the underside of the frame can sometimes make a lot of difference in this battle. Hold the torch for five or 10 minutes then try it again. 

Photo 35 shows the parts that make up the bottom bracket — the axel, two bearing rings, a lock nut and two bearings. Close inspection of the axel will reveal that one side is slightly longer than the other. The long side is the side to which the chain ring attaches, and the extra length is to help the chain ring clear the frame.

Photo 35 - Parts that make up a three-piece crank set.

The cup without the lock nut is also on the chain ring side and is a reverse thread, and the one with the lock nut is on the left side of the frame with right hand threads. Bearings always face into the cups so that the balls are in first, and the flat side is against the axel (Photo 36). If you are not sure which way to put bearings back together, just try it.

One way will have low friction even if you press as hard as you can. The other way will result in metal against metal, and it will feel a little stiff or harder to turn as you push on it. Now, the only parts left on the frame should be the bearing cups.

Photo 36 - Bearings only fit one way into the cup (balls down).

Find a rod or piece of metal long enough to reach into the head tube and get your hammer ready. Place your rod or screwdriver down the tube so it catches on the edge of one of the cups (Photo 37).

Because they are just pressed to fit, a few whacks with the hammer should get them out with little effort. It is the same process for the bottom bracket cups as it is for the head tube cups. If you have an old seat post lying around, this works great for hammering out the bearing cups. Most bottom bracket cups are the same, but fork bearing cups come in many different sizes.

BMX and heavy mountain bike frames have larger head tubes than light racing frames and kids bikes. The cup should require a hammer to put it into the frame. If it just slides in with little effort, then it is probably too small. Of course, you shouldn’t have to smash it in with a sledgehammer either!

Photo 37 - Banging out the head tube bearing cups.

Congratulations, you have taken a bike apart right down to the frame. If you plan on collecting a lot of bikes for your “scrap pile” then this is the best way to organize the parts. Separate all like parts into large plastic tubs such as pedals, or cranks, and put bearings, chains, and small parts in a tub with Varsol or another metal cleaner until they are free of rust and grime. Bikes take up a lot less space like this, and you can even hang all the frames on a wire like a clothesline out of the way. 

Not every bike you acquire will be in good shape. In fact, unless you plan on paying top dollar at yard sales and auctions, most of the bikes you get for free will be bent, rusted, worn, dented and generally beat up. But the best part is that you can get some decent frames and parts for free!

The good news is that most of the time the good parts will still be in tact, even after the bulldozer at the local landfill site mows the bike into a 20-foot tall twisted heap of scrap metal. Many of the projects in this book only use part of the frame, and some use none of the frame tubing at all, only pieces like the bottom bracket, head tube, and rear dropouts and other parts that you generally can’t make easily. 

When you can buy a 10-foot length of 1-inch thin-walled electrical conduit for $5, why mess around with rusty, dented frame tubing? Sometimes I’ll find an old bike at the scrap yard and chop it up right on the spot. I rarely use the frame tubing in my work. Now that you see what I am getting at here, let’s refer to Photo 038. Each number shows you the best order in which to chop a frame to bits. Numbers 1, 2, 3 and 4 are actually two cuts each. Since there are two legs to each part, you will cut them both.

Photo 38 - Cutting order for chopping up the frame.

It is a good idea to hold the frame securely in a vice or with a clamp to the workbench so it’s secure while you cut. It is very easy to snap a hacksaw blade if the work you are trying to cut turns and snags the blade (Photo 39).

Photo 39 - Cutting is easier when the frame is held securely in place.

If you are using a grinder with a cut-off wheel and your frame is not securely held in place, this can send the frame or your grinder flying across the room. Also, when gripping the frame tubes in the vice, don’t overdo it and crush the thin walls, unless you plan on discarding them anyway. Bicycle tubing is fairly thin and will flatten easily.

You can use a hacksaw or a grinder to make the cuts, but try to keep each cut as close to the joint as possible. This will ensure that the maximum length of frame is available, and it will be much less work to grind the stubs from the bottom bracket and head tube, especially if you plan to use a hand file to clean up the left over metal (Photo 40).

Photo 40 - Cutting close to the joint prevents excessive filing or grinding later on.

I’ve suggested a numerical order to the cuts (refer back to Photo 38) so you will be able to get your blade as close as possible to the tube joint without sawing in an awkward position. If you attempted to cut the seat tube first, the saw would hit against the chain stays or down tube and prevent a flush cut.

Hacks awing is an art in itself and once mastered, you will be able to cut off a tube right down to the base in a straight, even line without any problem at all. One thing to avoid when using a hacksaw is “speed cutting.” — one stroke per second is a good pace to use. This method will allow you to guide the cut into a straight line or along a marked path. If you saw away like crazy, the cut will be crazy or you will snap the blade very quickly.

When using a cutoff wheel for your grinder, be careful when you cut into a “triangle” or any part of the frame that is still a solid structural shape. Many times after the first cut into a “triangle” such as cuts #1 and #5 in Photo 38, the space made by the saw or grinder will try to collapse, thus catching the blade and causing it to snag. If this happens while using your grinder, it could fly out of your hands if you aren’t holding it tightly, so be aware. If this becomes a problem, just stop cutting with the grinder right before the end, then finish the cut with a hacksaw.

Photo 41 - All frame members separated after cutting.

When you have finished cutting, you should have a nice pile of tubing and various bike bits on the bench (see Photo 41). The more old frames you can collect, the easier it will be to make whatever you want as your creative energy kicks into gear. 

Throw away any badly bent tubing, and organize the rest for later use. Now we need to grind the leftover stubs from the bottom bracket and head tube. These are the most useful parts when making a custom frame of any kind. Set the part into a solid vice with the stub facing upwards and begin by grinding the end closest to you without digging into the good part. For this job, use a proper grinding wheel, not the cut off wheel, which is very thin and not made for side grinding, as seen in Photo 42.

Photo 42 - Grinding stubs off of the bottom bracket.

As you get the stub ground off, turn the work a little more and keep on going until all of the access tubing has been removed.  Be careful not to take too much off or you will make the bracket or head tube too thin. When you are done, the piece won’t look perfect, but it should still be fairly clean and round.

If you really want a clean job, grind until there is a small amount of stub left, then take it off with a hand file. Most of the time this is not necessary because you will be welding another tube back onto the rough area soon enough anyway. You will notice that most bottom brackets and head tubes have small holes where the tube meets. This is normal. These are breathing holes that allow moisture to escape from inside the tube, preventing rust from forming inside the tube. If there are holes that seem to be as large as the frame tubes, or the entire frame looks like it was made from one giant tube, what you have is a “lug-type” frame where one tube actually fits into another. These frames were very common in older 10-speed type bikes.

With this type of frame, the bottom brackets and head tubes are no good because after grinding, there will be a large holes in them where the tubes were removed. If you have a frame like this, the only useful parts are the frame tubing and the rear dropouts, so avoid these types if you can, or keep them for other projects that require an uncut frame.
Since you have the grinder out, now is a good time to trim the bottom brackets up as well.

Put them in the vice and trim off the last bit of tubing left over from the cutting. Don’t worry about the paint — this will burn right off during welding. Tubes and larger parts can be cleaned up with a wire wheel on your grinder as well.

Photo 43 - These are the building blocks for many projects that you will create.

When you are all done grinding, the parts will be clean of any stubs or welds and ready to be turned into whatever you like (Photo 43). 

Now that you’ve learned how to get the “meat” from an old frame in this chapter, you should never refuse any bike parts in any condition because there will always be something for the hard-core bike builder to use. 

With a little imagination and a stockpile of ready-to-weld parts, you can make just about any type of custom bike, such as the radical choppers presented in the following sections. Your initial attempts may not be completely successful, but at least you didn’t have to search for three months to get all of the parts. You’re ready to start building!


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